/Engine/Source/Runtime/Navmesh/Public/DetourCrowd/DetourPathCorridor.h
The path can be invalidated if there are structural changes to the underlying navigation mesh, or the state of a polygon within the path changes resulting in it being filtered out. (E.g. An exclusion or inclusion flag changes.)
bool isValid ( const int maxLookAhead, [dtNavMeshQuery](API\Runtime\Navmesh\Detour\dtNavMeshQuery) * navquery, const [dtQueryFilter](API\Runtime\Navmesh\Detour\dtQueryFilter) * filter )